question

(-1)^n-(1)^n=

$(-1)^n-(1)^n= (-1)^n - 1$

Thanks Heureka,

I'll go one step further:

$(-1)^n-(1)^n= (-1)^n - 1$

If n is even then this is      1-1=0

if n is odd then this is        -1-1=-2